cardiff: Improving rampup printing

Adding rampup information inside the header of this job:

A typical output looks like:
    ########## Rampup: 6 / 81 hosts #########

    Group 0 : Checking CPU perf
    loops_per_sec                     : SUMMARY :   6 consistent hosts with 834.00      as average value and    12.78 standard deviation : NO PERF ENTRY IN DB for Intel Xeon E312xx (Sandy Bridge)
    CPU Efficiency                    : SUMMARY :   6 consistent hosts with  50.00 %    as average value and     0.00 standard deviation
    ##########################################